Mesquite Flat Sand Dunes, Death Valley National Park. Photo: Jeffrey St. Clair.

I think of climate as a package in 3 basic parts – temperature, water, and wind. Here in the US, this trio is basic to the Forest Service “Hot Dry Windy Index” for measuring likely risk of dangerous wildfire.

The future of temperature is a key point of interest, because increased heat can make a difference to other parts of the package. Jason Smerdon, a Lamont-Doherty paleoclimatologist, provides an example in plain language — “Precipitation is just the supply side. Temperature is on the demand side, the part that dries things out.”

How high might temperatures go?

One climate model’s peek down the road shows a world with temperatures 2.4C hotter than back before we started setting the torch to coal, oil, and gas.

Another model shows us a possibility of getting 2.7C hotter, while yet another points to the possibility of heat increased to 3.1C over and above temperatures common to the 1850s

An attention-getting article of some years back warned of a “Hothouse Earth” at 5C. There’s even been a more recent study suggesting that we might, just maybe, if worse comes to worst, be on course to barreling past 3.5C on our way to 7C.

Given this smorgasbord of possible futures, it’s utterly realistic to be thinking about uncertainty. After all, the fact of disagreements among the models is plain to see.

And yet, at the same time, it’s equally plain that these varied and otherwise disagreeing models all agree on the direction we’re headed – toward and increasingly into a hotter world. This agreement leaves some elbow room for thinking about a bit of certainty in the mix.

The thing about models

Anyone who’s built a model car, plane, ship or train can be certain of two truths about models. They aren’t the real thing. They’re judged on how well they match up to the real thing. It’s basically the same for climate models.

The building of climate models has been going on for a long time. Consider the case of Svante Arrhenius, in the 1890s, for example. Arrhenius has been credited with playing a leading role in uniting physicists and chemists to recognize a new scientific topic for scientific thought, physical chemistry.

Based on the model he built, the crudest, most-simplistic model in the history of climate science, just a back-of-the-envelope kind of thing, Arrhenius concluded that an increasing scale of fossil fuel combustion would leave the world hotter-enough to make things hard for the likes of snow.

Has Arrhenilus’ model matched up with the real world?

In essence, Arrhenius’ crude little 1890s model pointed ahead to some future world hot enough to make snow an endangered form of water.

The current real-world low flows of the Colorado River have been traced back to loss of snow. Low flows in Montana rivers are traceable back to the same thing – a shortage of snow. There’s nuance here, and detail. But an increasing retreat of snow is a real thing, in lots of places, and Arrhenius wasn’t the last to think about it.

The April 20, 2004 Issue of Science published interviews with researchers known for investigating the future of snow. One researcher told Science that, “Snow is our water storage in the West,” and where snow is lost there is no way to make up for it.

Arrhenius likely had to shovel snow during winters in his home country, Sweden. Maybe that’s why he noted that life with less snow looked pretty good.

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